嵌入式linux通用截图工具

嵌入式linux通用截图工具

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文章出处：http://www.limodev.cn/blog
作者联系方式：李先静 <xianjimli at hotmail dot com>

为了截几张图片给broncho的A1做宣传，昨天写了一个截图工具。这个工具与其它截图工具不同的是，它不基于任何具体的GUI，直接从framebuffer中截图，然后保存为jpeg图片，所以适用于任何嵌入式linux设备。

o 打开framebuffer

static int fb_open(struct FB *fb, const char* fbfilename)
{
	fb->fd = open(fbfilename, O_RDWR);
	if (fb->fd < 0)
	{
		fprintf(stderr, "can't open %s/n", fbfilename);
		return -1;
	}
 
	if (ioctl(fb->fd, FBIOGET_FSCREENINFO, &fb->fi) < 0)
		goto fail;
	if (ioctl(fb->fd, FBIOGET_VSCREENINFO, &fb->vi) < 0)
		goto fail;
 
	fb->bits = mmap(0, fb_size(fb), PROT_READ | PROT_WRITE, 
					MAP_SHARED, fb->fd, 0);
	if (fb->bits == MAP_FAILED)
		goto fail;
 
	return 0;
fail:
	printf("%s is not a framebuffer./n", fbfilename);
	close(fb->fd);
 
	return -1;
}

o 读取数据并写入jpeg

static int snap(const char * filename, int quality, struct FB* fb)
{
	int row_stride = 0; 
	FILE * outfile = NULL;
	JSAMPROW row_pointer[1] = {0};
	struct jpeg_error_mgr jerr = {0};
	struct jpeg_compress_struct cinfo = {0};
 
	cinfo.err = jpeg_std_error(&jerr);
	jpeg_create_compress(&cinfo);
 
	if ((outfile = fopen(filename, "wb+")) == NULL) 
	{
		fprintf(stderr, "can't open %s/n", filename);
 
		return -1;
	}
 
	jpeg_stdio_dest(&cinfo, outfile);
	cinfo.image_width = fb_width(fb);
	cinfo.image_height = fb_height(fb);
	cinfo.input_components = 3;
	cinfo.in_color_space = JCS_RGB;
	jpeg_set_defaults(&cinfo);
	jpeg_set_quality(&cinfo, quality, TRUE);
	jpeg_start_compress(&cinfo, TRUE);
 
	row_stride = fb_width(fb) * 2;
	JSAMPLE* image_buffer = malloc(3 * fb_width(fb));
 
	while (cinfo.next_scanline < cinfo.image_height) 
	{
		int i = 0;
		unsigned short* line = fb->bits + cinfo.next_scanline * fb_width(fb);
		for(i = 0; i < fb_width(fb); i++)
		{
			int offset = i * 3;
			unsigned short color = line[i];
			unsigned char r = ((color >> 11) & 0xff) << 3;
			unsigned char g = ((color >> 5) & 0xff)  << 2;
			unsigned char b = (color & 0xff )<< 3;
			image_buffer[offset]     = r;
			image_buffer[offset + 1] = g;
			image_buffer[offset + 2] = b;
		}
 
		row_pointer[0] = image_buffer;
		(void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
	}
 
	jpeg_finish_compress(&cinfo);
	fclose(outfile);
 
	jpeg_destroy_compress(&cinfo);
 
	return 0;
}

o 主函数

int main(int argc, char* argv[])
{
	struct FB fb = {0};
	const char* filename   = NULL;
	const char* fbfilename = NULL;
 
	if(argc != 3)
	{	
		printf("/nusage: %s [jpeg] [framebuffer]/n", argv[0]);
		printf("-----------------------------------------/n");
		printf("Powered by broncho(www.broncho.cn)/n");
		return 0;
	}
 
	filename   = argv[1];
	fbfilename = argv[2];
	if (fb_open(&fb, fbfilename) == 0)
	{
		snap(filename, 100, &fb);
		fb_close(&fb);
	}
 
	return 0;
}

完整代码请到这里下载。